Enormous medical and technical progress has been made in detecting, treating, and reducing the adverse impact of nearly all other sensory impairments, except for loss of the sense of balance. Time and training in compensatory skills can help ameliorate some of the life-altering effects of this syndrome for patients with mild to moderate symptoms. At present, however, there is no approved or standardized therapeutic device available for those with chronic balance loss due to vestibulo-cerebellar dysfunction. The overall objective of this project is to develop a practical, wearable, cosmetically acceptable substitute for vestibular information that will improve the postural and functional abilities of these individuals. The BrainPort balance device presents head-postural information via electrotactile stimulation to the superior surface of the tongue. The subject then uses this tactile information to obtain correct head and body alignment and maintain balance. After training with the BrainPort balance device, adult subjects with severe balance loss due to various forms of vestibular dysfunction exhibited improved balance and postural control, as evidenced by a reduction in the number of falls and increased composite scores on standardized posturographic tests (NeuroCom CDP). Subjects also retain improved balance control for up to 6 hours after a 20-minute training session, and exhibited functional transfer to more stable and symmetric gait. Our objective in this Phase-2.2 project is to expand the applicability of the BrainPort balance device under the following Specific Aims: (1) to evolve and refine the BrainPort balance device by implementing a Pulse- Width-Modulation method of the electrotactile stimulation, (2) recruit and train subjects with severe chronic balance deficit due to central and mixed vestibulo-cerebellar etiologies, and (3) standardize and optimize the regimen for training these clinical populations using the current program as a template. We hypothesize that people with chronic balance loss (affecting an estimated 18 million people in the US, including elderly) will be similarly aided by use of this system. The studies funded by SBIR Phase-1 & 2 clearly demonstrate the effectiveness of the BrainPort balance device. The proposed Phase-2.2 studies will confirm the effectiveness of pulse-width-modulation stimulation method, and better define the population of vestibular disorder patients that will derive benefit from this system. Ultimately, we envision that the BrainPort balance device will become a key component of a comprehensive vestibular therapy program. [unreadable] [unreadable] [unreadable]